Abstract

Vacancy ordered phases have been earlier shown to be rational approximants to one-dimensional quasicrystals. The orientation relation between gamma brass and quasicrystals has also been pointed out in earlier work. Hexagonal phases in Al-Cr, Al-Mn and Mg base alloys have been shown to have a c/a ratio close to 1.225 (=Frank's ratio) and thus display pseudocubic symmetry. The interrelationships among these three classes of structures is emphasised as derivatives of the BCC lattice